Replacement of bypass fuel lines...
 

My last injector is a little damp, as is the bypass hose and end "cap". As a preventive measure I'd like to replace all of the bypass hose from the filter to the first cylinder and then on back to the last and the end cap.
Must I use MB line? I've used 3/8" fuel injection line before but that was with a clamp and these appear to be held on with just friction.
Any tips for removing the old line and installing the new?
Do I have to bleed anything when I am done?

I've never seen anything but the MB line work very well. Usually anything else swells, softens, and leaks. I assume you could use fuel line if you could find any that small (2mm ID), but the stuff from Benz works great.

The only thing to watch for is etremely hard return lines -- the ones on my brother's 300SDL were so hard the snapped if you tried to flex them. Not leaking, but only a matter of time, so to speak. When I took them off, they snapped off at the tip of the nipples on the injectors, and I had to fracture off the remains there on the nipples in order to get the new ones on! Ripped one up before I realized what was going on.

Best way to remove them is to get a pair of needle nosed plier with a good sharp square edge to the jaws, and grab the line alongside the nipple on the injector. Get as much of the material in the jaws as you can -- don't grab the nipple -- and shear the hose off the side of the nipple by crushing and twisting. This will tear the side off, making it much easier to get the rest of the line off, especially if they have gotten hard.

To put them on, make sure the nipples are clean, then use the needle nosed pliers to grasp the line just above where the nipple will end up. Hold along the length, not across. Push the line down on the nipple, making sure it seats all the way down on the injector.

Note that a torn or porous line will dump large amounts of fuel, the IP overflow will back up and run out, too.

Peter

Shawnster,

You need to bleed nothing. The fuel and any air in these overflow lines is just returning to the fuel tank along with the overflow from the IP and the air purge hole in the top of the secondary fuel filter.

P E H

It works for me.
 

I've been using clear FDA type vinyl tubing for the return lines and fuel lines on a VW jetta diesel for years and I have never had a problem with it. Any serious plumbing supplies place should have this tubing in many sizes on rolls. After about 5 years it starts to get stiff and I replace it, but I don't recall it ever leaking. I recently put it on a 300D. I think I used a 3/32" ID line for the injectors and heated the ends a little so they go on the nipples easier. I like being able to see the fuel in the lines.

Now for the disclaimer! I would NEVER use this for gasoline and it is not "approved" for diesel fuel as far as I know, so use your own judgement .

i have never had any luck with using other than MB line. it is rather expensive (at least i thought so..) but fact is that it works and does not leak.:cool:

I believe you can get the correct hose for about $5.00 per meter from one or more of the Mercedes parts suppliers on the internet. However, if that's all you're getting then shipping will probably double your cost. My local diesel shop had the correct hose for about $9.00 per yard so you may be able to find it locally as well.

I've been using black fuel line , I think 2.5 mm ID, for about two years now and no leaks. So far, the lines still feel like they did when new and only cost about $.50. I want to replace with the braided stuff but Fastlane has been out everytime I ordered it so I haven't.

I just did the job tonight. It requires about 1 1/2 meters. I would suggest that you take a razor and slice the outer fabric at the nipple to make it easier to pull off, otherwise it will tear and a little bit will remain at the nipple. Do it while the engine is warm (not hot!) and the hose will slide on easily.

Just be careful if you decide to cut the fabric outer coating. If you cut too far and go through the rubber you could also score the barbs on the injector nipple. This can keep your new hose from sealing well against the injector barb and has been the cause of many mysterious leaks.